Compressor sensor module

ABSTRACT

A sensor module for a compressor having an electric motor connected to a power supply is provided. The sensor module includes an input that receives current measurements generated by a current sensor based on a current of the power supply. The sensor module also includes a processor. The processor is connected to the input, determines a maximum continuous current for the electric motor, and selectively compares the current measurements with a value equal to the maximum continuous current multiplied by a predetermined value. The maximum continuous current is set based on at least one of a type of refrigerant used by the compressor and actual refrigeration system conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 12/261,643, filed on Oct. 30, 2008, which claims the benefit of U.S. Provisional Application No. 60/984,902, filed on Nov. 2, 2007. The entire disclosures of the above applications are incorporated herein by reference.

FIELD

The present disclosure relates to compressors, and more particularly, to a compressor with a sensor module.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Compressors are used in a variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system (generically “refrigeration systems”) to provide a desired heating or cooling effect. Compressors may include an electric motor to provide torque to compress vapor refrigerant. The electric motor may be powered by an alternating current (AC) or direct current (DC) power supply. In the case of an AC power supply, single or poly-phase AC may be delivered to windings of the electric motor. For example, the compressor may include an electric motor configured to operate with three phase AC. The electric motor may include at least one set of windings corresponding to each of the three phases.

In each application, it is desirable for the compressor to provide consistent and efficient operation to ensure that the refrigeration system functions properly. Variations in the supply of electric power to the electric motor of the compressor may disrupt operation of the electric motor, the compressor, and the refrigeration system. Such variations may include, for example, excessive, or deficient, current or voltage conditions. In the case of a poly-phase AC power supply, such variations may include an unbalanced phase condition wherein the current or voltage of at least one phase of AC is excessively varied from the current or voltage of the other phases. Further, such variations may include a loss of phase condition wherein one phase of AC is interrupted while the remaining phases continue to be delivered. Excessive current or voltage conditions may cause the electric motor to overheat which may damage the electric motor or the compressor. Deficient current or voltage conditions, unbalanced phase conditions, and loss of phase conditions may disrupt operation of the electric motor, the compressor, or the refrigeration system and cause unnecessary damage.

The electric motor of a compressor may be equipped with a temperature or current sensor to detect overheating of the electric motor during electrical power disturbances. For example, a bi-metallic switch may trip and deactivate the electric motor when the electric motor is overheated or drawing excessive electrical current. Such a system, however, does not detect variations in the power supply that may not immediately or drastically increase the temperature of the electric motor. In addition, such systems may not detect a variation in electrical power until the condition has increased the temperature of the electric motor or the electric motor windings.

Further, such systems do not provide sufficient data to evaluate electrical efficiency of the electric motor overall. Variations in the supply of electric power may result in inefficient operation of the compressor, the electric motor, or the refrigeration system. Refrigeration systems generally require a significant amount of energy to operate, with energy requirements being a significant cost to retailers. As a result, it is in the best interest of retailers to closely monitor the supply of electric power to their refrigeration systems to maximize efficiency and reduce operational costs.

SUMMARY

In a feature, a sensor module for a compressor having an electric motor connected to a power supply is provided. The sensor module includes an input that receives current measurements generated by a current sensor based on a current of the power supply. The sensor module also includes a processor. The processor is connected to the input, determines a maximum continuous current for the electric motor, and selectively compares the current measurements with a value equal to the maximum continuous current multiplied by a predetermined value. The maximum continuous current is set based on at least one of a type of refrigerant used by the compressor and actual refrigeration system conditions.

In a feature, a sensor module for a compressor having an electric motor connected to a power supply is provided. The sensor module includes an input that receives current measurements generated by a current sensor based on a current of the power supply. The sensor module also includes a processor that is connected to the input, that determines a maximum continuous current for the electric motor set based on actual refrigeration system conditions, and that selectively compares the current measurements with a value equal to the maximum continuous current multiplied by a predetermined value.

In a feature, a method performed by a sensor module for a compressor having an electric motor connected to a power supply is provided. The method includes receiving current measurements generated by a current sensor based on a current of the power supply. The method further includes: determining a maximum continuous current for the electric motor set based on at least one of a type of refrigerant used by the compressor and actual refrigeration system conditions; and selectively comparing the current measurements with a value equal to the maximum continuous current multiplied by a predetermined value.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a schematic view of a refrigeration system;

FIG. 2 is a schematic view of a compressor with a sensor module and a control module;

FIG. 3 is a schematic view of a compressor with a sensor module and a control module;

FIG. 4 is a schematic view of a compressor with a sensor module and a control module;

FIG. 5 is a perspective view of a compressor with a sensor module and a control module;

FIG. 6 is a top view of a compressor with a sensor module and a control module;

FIG. 7 is a schematic view of an electrical enclosure of a compressor including a sensor module;

FIG. 8 is a schematic view of an electrical enclosure of a compressor including a sensor module;

FIG. 9 is a schematic view of an electrical enclosure of a compressor including a sensor module;

FIG. 10 is a schematic view of an electrical enclosure of a compressor including a sensor module;

FIG. 11 is a schematic view of an electrical enclosure of a compressor including a sensor module;

FIG. 12 is a schematic view of an electrical enclosure of a compressor including a sensor module;

FIG. 13 is a flow chart illustrating an operating algorithm of a sensor module in accordance with the present teachings;

FIG. 14 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 15 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 16 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 17 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 18 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 19 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 20 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 21 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;

FIG. 22 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings; and

FIG. 23 is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

As used herein, the terms module, control module, and controller refer to one or more of the following: an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality. Further, as used herein, computer-readable medium refers to any medium capable of storing data for a computer. Computer-readable medium may include, but is not limited to, memory, RAM, ROM, PROM, EPROM, EEPROM, flash memory, punch cards, dip switches, CD-ROM, floppy disk, magnetic tape, other magnetic medium, optical medium, or any other device or medium capable of storing data for a computer.

With reference to FIG. 1, an exemplary refrigeration system 10 may include a plurality of compressors 12 piped together with a common suction manifold 14 and a discharge header 16. Compressor 12 may be a reciprocating compressor, a scroll type compressor, or another type of compressor. Compressor 12 may include a crank case. Compressors 12 may be equipped with electric motors to compress refrigerant vapor that is delivered to a condenser 18 where the refrigerant vapor is liquefied at high pressure, thereby rejecting heat to the outside air. The liquid refrigerant exiting the condenser 18 is delivered to an evaporator 20. As hot air moves across the evaporator, the liquid turns into gas, thereby removing heat from the air and cooling a refrigerated space. This low pressure gas is delivered to the compressors 12 and again compressed to a high pressure gas to start the refrigeration cycle again. While a refrigeration system 10 with two compressors 12, a condenser 18, and an evaporator 20 is shown in FIG. 1, a refrigeration system 10 may be configured with any number of compressors 12, condensers 18, evaporators 20, or other refrigeration system components.

Each compressor 12 may be equipped with a control module (CM) 30 and a sensor module (SM) 32. As described herein, SM 32 may be affixed to compressor 12 and may monitor electric power delivered to compressor 12 with one or more voltage sensors and one or more current sensors. Based on electrical power measurements, such as electric current (I) and voltage (V), SM 32 may determine apparent power, actual power, power consumption, and power factor calculations for the electric motor of compressor 12. SM 32 may communicate the electric power measurements and calculations to CM 30. SM 32 may also alert CM 30 of variations in the power supply, or of mechanical failures, based on the measurements and calculations. For example, SM 32 may alert CM 30 of an excessive current or voltage condition, a deficient current or voltage condition, a current or voltage imbalance condition, or a loss of phase or current delay condition (if poly-phase electric power is used). Based on the monitoring of the electric power supply and based on the communication with CM 30, SM 32 may detect and alert CM 30 to a welded contactor condition, or a locked rotor condition.

CM 30 may control operation of compressor 12 based on data received from SM 32, based on other compressor and refrigeration system data received from other compressor or refrigeration system sensors, and based on communication with a system controller 34. CM 30 may be a protection and control system of the type disclosed in assignee's commonly-owned U.S. patent application Ser. No. 11/059,646, Publication No. 2005/0235660, filed Feb. 16, 2005, the disclosure of which is incorporated herein by reference. Other suitable protection and control systems may be used.

In addition to the data received by CM 30 from SM 32, CM 30 may receive compressor and refrigeration system data including discharge pressure, discharge temperature, suction pressure, suction temperature, and other compressor related data from pressure and temperature sensors connected to or, embedded within, compressor 12. In addition, oil level and oil pressure data may be received by SM 32 and communicated to CM 30 and/or received by CM 30 directly. In this way, CM 30 may monitor the various operating parameters of compressor 12 and control operation of compressor 12 based on protection and control algorithms and based on communication with system controller 34. For example, CM 30 may activate and deactivate the compressor 12 according to a set-point, such as a suction pressure, suction temperature, discharge pressure, or discharge temperature set-point. In the case of a discharge pressure set-point, CM 30 may activate compressor 12 when the discharge pressure, as determined by a discharge pressure sensor, falls below the discharge pressure set-point. CM 30 may deactivate compressor 12 when the discharge pressure rises above the discharge pressure set-point.

Further, CM 30 may activate or deactivate compressor 12 based on data and/or alerts received from SM 32. For example, CM 30 may deactivate compressor 12 when alerted of an excessive current or voltage condition, a deficient current or voltage condition, a current or voltage imbalance condition, or a loss of phase or current delay condition (if poly-phase electric power is used). Further, CM 30 may activate compressor 12 when alerted of a welded contactor condition or deactivate compressor 12 when alerted of a locked rotor condition. CM 30 may communicate operating data of compressor 12, including electric power data received from SM 32, to system controller 34.

In this way, SM 32 may be specific to compressor 12 and may be located within an electrical enclosure 72 of compressor 12 for housing electrical connections to compressor 12 (shown in FIGS. 5-12) at the time of manufacture of compressor 12. CM 30 may be installed on compressor 12 after manufacture and at the time compressor 12 is installed at a particular location in a particular refrigeration system, for example. Different control modules may be manufactured by different manufacturers. However, each CM 30 may be designed and configured to communicate with SM 32. In other words, SM 32 for a particular compressor 12 may provide data and signals that can be communicated to any control module appropriately configured to communicate with SM 32. Further, manufacturers of different control modules may configure a control module to receive data and signals from SM 32 without knowledge of the algorithms and computations employed by SM 32 to provide the data and signals.

System controller 34 may be used and configured to control the overall operation of the refrigeration system 10. System controller 34 is preferably an Einstein Area Controller offered by CPC, Inc. of Atlanta, Ga., or any other type of programmable controller that may be programmed to operate refrigeration system 10 and communicate with CM 30. System controller 34 may monitor refrigeration system operating conditions, such as condenser temperatures and pressures, and evaporator temperatures and pressures, as well as environmental conditions, such as ambient temperature, to determine refrigeration system load and demand. System controller 34 may communicate with CM 30 to adjust set-points based on operating conditions to maximize efficiency of refrigeration system 10. System controller 34 may evaluate efficiency based on electric power measurements and calculations made by SM 32 and communicated to system controller 34 from CM 30.

With reference to FIG. 2, three phase AC electric power 50 may be delivered to compressor 12 to operate an electric motor. SM 32 and CM 30 may receive low voltage power from one of the phases of electric power 50 delivered to compressor 12. For example, a transformer 49 may convert electric power 51 from one of the phases to a lower voltage for delivery to SM 32 and CM 30. In this way, SM 32 and CM 30 may operate on single phase AC electric power at a lower voltage than electric power 50 delivered to compressor 12. For example, electric power delivered to SM 32 and CM 30 may be 24V AC. When low voltage power, for example 24V AC, is used to power CM 30 and SM 32, lower voltage rated components, such as lower voltage wiring connections, may be used.

SM 32 may be connected to three voltage sensors 54, 56, 58, for sensing voltage of each phase of electric power 50 delivered to compressor 12. In addition, SM 32 may be connected to a current sensor 60 for sensing electric current of one of the phases of electric power 50 delivered to compressor 12. Current sensor 60 may be a current transformer or current shunt resistor.

When a single current sensor 60 is used, electric current for the other phases may be estimated based on voltage measurements and based on the current measurement from current sensor 60. Because the load for each winding of the electric motor may be substantially the same as the load for each of the other windings, because the voltage for each phase is known from measurement, and because the current for one phase is known from measurement, current in the remaining phases may be estimated.

Additional current sensors may also be used and connected to SM 32. With reference to FIG. 3, two current sensors 57, 60 may be used to sense electric current for two phases of electric power 50. When two current sensors 57, 60 are used, electric current for the remaining phase may be estimated based on voltage measurements and based on the current measurements from current sensors 57, 60. With reference to FIG. 4, three current sensors 55, 57, 60 may be used to sense electric current for all three phases of electric power 50.

In the case of a dual winding three phase electric motor, six electrical power terminals may be used, with one terminal for each winding resulting in two terminals for each of the three phases of electric power 50. In such case, a voltage sensor may be included for each of the six terminals, with each of the six voltage sensors being in communication with SM 32. In addition, a current sensor may be included for one or more of the six electrical connections.

With reference to FIGS. 5 and 6, CM 30 and SM 32 may be mounted on or within compressor 12. CM 30 may include a display 70 for graphically displaying alerts or messages. As discussed above, SM 32 may be located within electrical enclosure 72 of compressor 12 for housing electrical connections to compressor 12.

Compressor 12 may include a suction nozzle 74, a discharge nozzle 76, and an electric motor disposed within an electric motor housing 78.

Electric power 50 may be received by electrical enclosure 72. CM 30 may be connected to SM 32 through a housing 80. In this way, CM 30 and SM 32 may be located at different locations on or within compressor 12, and may communicate via a communication connection routed on, within, or through compressor 12, such as a communication connection routed through housing 80.

With reference to FIGS. 7 through 12, SM 32 may be located within electrical enclosure 72. In FIGS. 7 through 12, a schematic view of electrical enclosure 72 and SM 32 is shown. SM 32 may include a processor 100 with RAM 102 and ROM 104 disposed on a printed circuit board (PCB) 106. Electrical enclosure 72 may be an enclosure for housing electrical terminals 108 connected to an electric motor of compressor 12. Electrical terminals 108 may connect electric power 50 to the electric motor of compressor 12.

Electrical enclosure 72 may include a transformer 49 for converting electric power 50 to a lower voltage for use by SM 32 and CM 30. For example, electric power 51 may be converted by transformer 49 and delivered to SM 32. SM 32 may receive low voltage electric power from transformer 49 through a power input 110 of PCB 106. Electric power may also be routed through electrical enclosure 72 to CM 30 via electrical connection 52.

Voltage sensors 54, 56, 58 may be located proximate each of electrical terminals 108. Processor 100 may be connected to voltage sensors 54, 56, 58 and may periodically receive or sample voltage measurements. Likewise, current sensor 60 may be located proximate one of electrical power leads 116. Processor 100 may be connected to current sensor 60 and may periodically receive or sample current measurements. Electrical voltage and current measurements from voltage sensors 54, 56, 58 and from current sensor 60 may be suitably scaled for the processor 100.

PCB 106 may include a communication port 118 to allow communication between processor 100 of SM 32 and CM 30. A communication link between SM 32 and CM 30 may include an optical isolator 119 to electrically separate the communication link between SM 32 and CM 30 while allowing communication. Optical isolator 119 may be located within electrical enclosure 72. Although optical isolator 119 is independently shown, optical isolator 119 may also be located on PCB 106. At least one additional communication port 120 may also be provided for communication between SM 32 and other devices. A handheld or portable device may directly access and communicate with SM 32 via communication port 120. For example, communication port 120 may allow for in-circuit programming of SM 32 a device connected to communication port 120. Additionally, communication port 120 may be connected to a network device for communication with SM 32 across a network.

Communication with SM 32 may be made via any suitable communication protocol, such as I2C, serial peripheral interface (SPI), RS232, RS485, universal serial bus (USB), or any other suitable communication protocol.

Processor 100 may access compressor configuration and operating data stored in an embedded ROM 124 disposed in a tamper resistant housing 140 within electrical enclosure 72. Embedded ROM 124 may be a compressor memory system disclosed in assignee's commonly-owned U.S. patent application Ser. No. 11/405,021, filed Apr. 14, 2006, U.S. patent application Ser. No. 11/474,865, filed Jun. 26, 2006, U.S. patent application Ser. No. 11/474,821, filed Jun. 26, 2006, U.S. patent application Ser. No. 11/474,798, filed Jun. 26, 2006, or U.S. Patent Application No. 60/674,781, filed Apr. 26, 2005, the disclosures of which are incorporated herein by reference. In addition, other suitable memory systems may be used.

Embedded ROM 124 may store configuration and operating data for compressor 12. When configuration data for compressor 12 is modified, the modified data may likewise be stored in embedded ROM 124. Configuration data for compressor 12 may be communicated to CM 30 or system controller 34. When compressor and/or SM 32 are replaced, the default configuration data for the new compressor 12 may be communicated to CM 30 and/or system controller 34 upon startup. In addition, configuration data may be downloaded remotely. For example, configuration data in embedded ROM 124 may include operating and diagnostic software that may be upgraded via a network connection. In this way, operating and diagnostic software may be upgraded efficiently over the network connection, for example, via the internet.

Relays 126, 127 may be connected to processor 100. Relay 126 may control activation or deactivation of compressor 12. When SM 32 determines that an undesirable operating condition exists, SM 32 may simply deactivate compressor 12 via relay 126. Alternatively, SM 32 may notify CM 30 of the condition so that CM 30 may deactivate the compressor 12. Relay 127 may be connected to a compressor related component. For example, relay 127 may be connected to a crank case heater. SM 32 may activate or deactivate the crank case heater as necessary, based on operating conditions or instructions from CM 30 or system controller 34. While two relays 126, 127 are shown, SM 32 may, alternatively, be configured to operate one relay, or more than two relays.

Processor 100 and PCB 106 may be mounted within a housing enclosure 130. Housing enclosure 130 may be attached to or embedded within electrical enclosure 72. Electrical enclosure 72 provides an enclosure for housing electrical terminals 108 and transformer 49. Housing enclosure 130 may be tamper-resistant such that a user of compressor 12 may be unable to inadvertently or accidentally access processor 100 and PCB 106. In this way, SM 32 may remain with compressor 12, regardless of whether compressor 12 is moved to a different location, returned to the manufacturer for repair, or used with a different CM 30.

LED's 131, 132 may be located on, or connected to, PCB 106 and controlled by processor 100. LED's 131, 132 may indicate status of SM 32 or an operating condition of compressor 12. LED's 131, 132 may be located on housing enclosure 130 or viewable through housing enclosure 130. For example, LED 131 may be red and LED 132 may be green. SM 32 may light green LED 132 to indicate normal operation. SM 32 may light red LED 131 to indicate a predetermined operating condition. SM 32 may also flash the LED's 131, 132 to indicate other predetermined operating conditions.

In FIG. 7, one current sensor 60 is shown. Additional current sensors may also be used and connected to SM 32. With reference to FIG. 8, two current sensors 57, 60 may be used to sense electric current for two phases of electric power 50. When two current sensors 57, 60 are used, electric current for the remaining phase may be estimated based on voltage measurements and based on the current measurements from current sensors 57, 60. With reference to FIG. 9, three current sensors 55, 57, 60 may be used to sense electric current for all three phases of electric power 50.

With reference to FIGS. 10 to 12, in the case of a dual winding three phase electric motor, electrical enclosure 72 may include additional electrical terminals 109 for additional windings. In such case, six electrical terminals 108, 109 may be located within electrical enclosure 72. Three electrical terminals 108 may be connected to the three phases of electric power 50 for a first set of windings of the electric motor of compressor 12. Three additional electrical terminals 109 may also connected to the three phases of electric power 50 for a second set of windings of the electric motor of compressor 12.

Voltage sensors 61, 62, 63 may be located proximate each of electrical terminals 109. Processor 100 may be connected to voltage sensors 61, 62, 63 and may periodically receive or sample voltage measurements. With reference to FIG. 10, processor 100 may periodically receive or sample current measurements from a current sensor 64 for sensing electrical current flowing to one of the additional electrical terminals 109. Additional current sensors may also be used. With reference to FIG. 11, four current sensors 57, 60, 64, 65 may be connected to processor 100. Two current sensors 57, 60 may be associated with electrical terminals 108 and two current sensors 64, 65 may be associated with electrical terminals 109. With reference to FIG. 12, six current sensors 55, 57, 60, 64, 65, 66 may be connected to processor 100. Three current sensors 55, 57, 60 may be associated with electrical terminals 108 and three current sensors 64, 65, 66 may be associated with electrical terminals 109. With six current sensors 55, 57, 60, 64, 65, 66, processor 100 may receive current measurements for each winding of a dual winding three phase electric motor associated with compressor 12.

Processor 100 may sample current and voltage measurements from the various sensors periodically over each cycle of AC power to determine multiple instantaneous current and voltage measurements. For example, processor 100 may sample current and voltage measurements twenty times per cycle or approximately once every millisecond in the case of alternating current with a frequency of sixty mega-hertz. From these actual current and voltage measurements, processor 100 may calculate additional power related data such as true and apparent power, power consumption over time, and power factor.

Based on actual current and voltage measurements, processor 100 may determine a root mean square (RMS) value for voltage and current for each phase of electric power 50. Processor 100 may calculate an RMS voltage value by squaring each of the sampled voltage measurements, averaging the squared measurements, and calculating the square root of the average. Likewise, processor 100 may calculate an RMS current value by squaring each of the sampled current measurements, averaging the squared measurements, and calculating the square root of the average.

From RMS voltage and RMS current calculations, processor 100 may calculate apparent power (S) according to the following equation:

S=V _(RMS) ×I _(RMS),  (1)

where V_(RMS) is the calculated RMS of voltage over at least one cycle of AC and where I_(RMS) is the calculated RMS of current over at least one cycle of AC. Apparent power may be calculated in units of Volt-Amps (VA) or kilo-Volt-Amps (kVA)

Processor 100 may calculate apparent power for each phase of electric power 50. When current sensors 55, 57, 60, 64, 65, 66 are available for all three phases of electric power 50, actual current measurements may be used to calculate apparent power. When current sensors are not available for all three phases, current for a missing phase may be estimated by interpolation from known current and voltage measurements.

Processor 100 may calculate total apparent power (S_(Total)) for an electric motor of compressor 12 based on apparent power calculations for each of the phases, according to the following equation:

S _(Total) =V _(RMS(1)) ×I _(RMS(1)) +V _(RMS(2)) ×I _(RMS(2)) +V _(RMS(3)) ×I _(RMS(3)),  (2)

where V_(RMS(1)), V_(RMS(2)), and V_(RMS(3)) are the calculated RMS voltage over a cycle of AC for the first, second, and third phase of AC, respectively, and where I_(RMS(1)), I_(RMS(2)), and I_(RMS(3)) are the calculated RMS current a cycle of AC for the first, second, and third phase of AC, respectively. Apparent power is calculated in units of Volt-Amps (VA) or kilo-Volt-Amps (kVA)

Active power (P), in units of watts (W) or kilo-watts (kW) may be calculated as an integral of the product of instantaneous currents and voltages over a cycle of AC, according to the following equation:

$\begin{matrix} {{P = {\frac{1}{T}{\int_{0}^{T}{\left( {{v(t)}{i(t)}} \right){t}}}}},} & (3) \end{matrix}$

where v(t) is instantaneous voltage at time t, in units of volts; where i(t) is instantaneous current at time t, in units of amps; and where T is the period.

Based on the actual instantaneous electrical current and voltage measurements sampled over a cycle of the AC power, processor 100 may calculate (P) as the sum of the products of instantaneous voltage and current samples for each sample interval (e.g., one millisecond), over one cycle of AC. Thus, P may be calculated by processor 100 according to the following equation:

$\begin{matrix} {{P \cong {\frac{1}{T}{\sum\limits_{k = 1}^{k = \frac{T}{\Delta \; t}}{{v(k)}{i(k)}\Delta \; t}}}},} & (4) \end{matrix}$

where v(k) is the instantaneous voltage measurement for the kth sample; i(k) is the instantaneous current measurement for the kth sample; T is the period; and Δt is the sampling interval (e.g., 1 millisecond).

P may be calculated for each phase of electric power. Processor 100 may calculate a total active power (P_(Total) by adding the active power for each phase, according to the following equation:

P _(Total) =P ₍₁₎ +P ₍₂₎ +P ₍₃₎,  (5)

Where P₍₁₎, P₍₂₎, and P₍₃₎ are the active power for the first, second, and third phase of AC, respectively.

Based on the active power calculations, processor 100 may calculate energy consumption by calculating an average of active power over time. Energy consumption may be calculated by processor 100 in units of watt-hours (WH) or kilo-watt-hours (kWH).

Further, based on the active power calculation and the apparent power calculation, processor 100 may calculate the power factor (PF) according to the following equation:

$\begin{matrix} {{{PF} = \frac{P}{S}},} & (6) \end{matrix}$

where P is active power in units of watts (W) or kilo-watts (kW); and where S is apparent power in units of volt-amps (VA) or kilo-volt-amps (kVA). Generally, PF is the ratio of the power consumed to the power drawn. Processor 100 may calculate PF for each phase of electric power. Processor 100 may also calculate a total PF as a ratio of total actual power to total apparent power, according to the following equation:

$\begin{matrix} {{{PF}_{Total} = \frac{P_{Total}}{S_{Total}}},} & (7) \end{matrix}$

where P_(total) and S_(Total) are calculated according to formulas 2 and 5 above.

Alternatively, processor 100 may calculate power factor by comparing the zero crossings of the voltage and current waveforms. The processor may use the angular difference between the zero crossings as an estimate of PF. Processor 100 may monitor voltage and current measurements to determine voltage and current waveforms for electric power 50. Based on the measurements, processor may determine where each waveform crosses the zero axis. By comparing the two zero crossings, processor 100 may determine an angular difference between the voltage waveform and the current waveform. The current waveform may lag the voltage waveform, and the angular difference may be used by processor 100 as an estimate of PF.

PF may be used as an indication of the efficiency of the electric motor or the compressor. Increased lag between the current waveform and the voltage waveform results in a lower power factor. A power factor near one, i.e., a unity power factor, is more desirable than a lower power factor. An electric motor with a lower power factor may require more energy to operate, thereby resulting in increased power consumption.

SM 32 may provide continually updated power factor calculations, as well as RMS voltage, RMS current, active power, apparent power, and energy consumption calculations, based on continually sampled instantaneous electrical current and voltage measurements, to CM 30 and/or system controller 34. CM 30 and system controller 34 may utilize the electrical electric power measurements and calculations communicated from SM 32 to control and evaluate efficiency of compressor 12 or refrigeration system 10.

Further, electrical measurements and calculations, including PF, may be accessed by a user through system controller 34 or CM 30. Additionally, electrical measurements and calculations may be accessed through direct communication with SM 32 via communication port 120. Electrical measurements and calculations may be stored and periodically updated in embedded ROM 124.

In this way, electrical calculations and measurements, such as RMS voltage, RMS current, active power, apparent power, power factor, and energy calculations may be accurately and efficiently made at the compressor 12 and communicated to other modules or controllers or to a user of the compressor 12 or refrigeration system 10 for purposes of evaluating electrical power usage.

In addition to communicating electrical calculations and measurements to other modules, controllers, or users, SM 32 may use the electrical calculations and measurements diagnostically to detect certain variations in operating conditions. SM 32 may alert CM 30 to certain operating conditions based on the electrical calculations and measurements.

Referring now to FIG. 13, a flow chart illustrating an operating algorithm 1300 for SM 32 is shown. In step 1301, SM 32 may initialize. Initialization may include resetting counters, timers, or flags, checking and initializing RAM 102, initializing ports, including communication ports 118, 120, enabling communication with other devices, including CM 30, checking ROM 104, checking embedded ROM 124, and any other necessary initialization functions. SM 32 may load operating instructions from ROM 104 for execution by processor 100.

In step 1302, SM 32 may receive actual electrical measurements from connected voltage and current sensors. SM 32 may receive a plurality of instantaneous voltage and current measurements over the course of a cycle of the AC electrical power. SM 32 may buffer the voltage and current measurements in RAM 102 for a predetermined time period.

In step 1304, SM 32 may calculate RMS voltage and RMS current based on the instantaneous voltage and current measurements. Based on the RMS voltage and RMS current calculations, SM 32 may calculate apparent power in step 1304. Based on the instantaneous voltage and current measurements, SM 32 may also calculate active power. Based on the apparent power calculation and the active power calculation, SM 32 may calculate the power factor. SM 32 may also calculate the power factor from the instantaneous voltage and current measurements by examining an angular difference between the zero crossings of the electrical current waveform and the voltage waveform.

In step 1306, SM 32 may receive run state data from CM 30. The run state data may include data indicating whether an electric motor of compressor 12 is currently in an activated or deactivated state. The run state data may also include timing data indicating a period of time that the electric motor has been in the current state. If the electric motor is a dual winding three phase electric motor, the run state data may also including data indicating whether one or both of the windings are activated.

In step 1308, based on the electrical measurements and calculations, and based on the data received from CM 30, SM 32 may perform and/or monitor diagnostic algorithms as described in more detail below. Some diagnostic algorithms may be executed once per each iteration of operating algorithm 1300. Some diagnostic algorithms may be executed concurrently with, and monitored by, operating algorithm 1300.

In step 1310, SM 32 may communicate the results of the electrical measurements and calculations to CM 30. SM 32 may also communicate the results of any diagnostic algorithms to CM 30. As described below, SM 32 may set operating flags corresponding to operating conditions according to diagnostic algorithms. SM 32 may communicate any operating flags to CM 30 in step 1310.

In step 1312, SM 32 may receive and respond to communications from CM 30. For example, CM 30 may request particular data from SM 32. CM 30 may also request certain data from embedded ROM 124. CM 30 may update SM 32 with operating parameters or thresholds for use in diagnostic algorithms. CM 30 may direct SM 32 to activate or deactivate any compressor related devices, such as a crank case heater, controlled by SM 32 via relay 127.

After responding to communications from CM 30 in step 1312, SM 32 may loop back to step 1302 and continue operation.

Referring now to FIG. 14, a flow chart illustrating an algorithm 1400 for SM 32 to detect a no-power condition is shown. The algorithm 1400 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. Prior to execution of the algorithm 1400, a no-power flag may have been reset by SM 32.

In step 1401, SM 32 may determine whether the current run state is set to run, based on run state data received from CM 30, as described with reference to step 1306 of FIG. 13 above. When the run state is not set to run, compressor 12 is not activated, and SM 32 may end execution of the algorithm in step 1402.

When the run state is set to run, SM 32 may proceed to step 1404 and check voltage measurements. When three phase power is used, SM 32 may check each of three voltage measurements, V₁, V₂, and V₃. SM 32 may determine whether V₁, V₂, and V₃ are less than a minimum voltage threshold, V_(min-14). In step 1404, when V₁, V₂, and V₃ are greater than or equal to V_(min-14), SM 32 may determine that compressor 12 has sufficient power, and end execution of algorithm 1400 in step 1402.

In step 1404, when SM 32 determines that V₁, V₂, and V₃ are less than V_(min-14), SM 32 may proceed to step 1406. In step 1406, SM 32 may determine whether the time since the compressor 12 was activated is greater than a time threshold, Tm_(Thr-14). For example, Tm_(Thr-14) may be set to two seconds. In this way, SM 32 may allow for any bounce of any contactor coil relays. In step 1406, when the time since compressor activation is not greater than Tm_(Thr-14), SM 32 may return to step 1401.

In step 1406, when the time since compressor activation is greater than TM_(Thr-14), SM 32 may proceed to step 1408. In step 1408, SM 32 may set a no-power flag. By setting the no-power flag, SM 32 may indicate that compressor 12 does not have sufficient electrical power to operate. The no-power flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

Referring now to FIG. 15, a flow chart illustrating an algorithm 1500 for SM 32 to detect a welded contactor condition is shown. The algorithm 1500 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. Prior to execution of the algorithm 1500, a welded-contactor flag may have been reset by SM 32. A welded contactor may cause compressor 12 to continue to operate, even though SM 32 or CM 30 may have attempted to open a contactor to deactivate the compressor.

In step 1501, SM 32 may determine whether the current run state is set to run, based on run state data previously received from CM 30, as described with reference to step 1306 of FIG. 13 above. When the run state is set to run, the compressor 12 is activated, and SM 32 may end execution of the algorithm in step 1502.

When the run state is not set to run, SM 32 may proceed to step 1504 and check voltage measurements. When three phase power is used, SM 32 may check each of three voltage measurements, V₁, V₂, and V₃. SM 32 may determine whether voltages V₁, V₂, or V₃ are greater than a maximum voltage threshold, V_(max-15). In step 1504, when V₁, V₂, or V₃ are not greater than or equal to V_(max-15), SM 32 may determine that a welded contactor condition does not exist, and end execution of the algorithm in step 1502.

When V₁, V₂, or V₃ are greater than V_(max-15), SM 32 may proceed to step 1506. In step 1506, SM 32 may determine whether the time since compressor 12 was deactivated is greater than a time threshold, Tm_(Thr-15). For example, Tm_(Thr-15) may be set to two seconds. By waiting for the Tm_(Thr-15), SM 32 may allow for any bounce of any contactor coil relays. In step 1506, when the time since compressor deactivation is not greater than Tm_(Thr-15), SM 32 may return to step 1501.

In step 1506, when the time since compressor deactivation is greater than TM_(Thr-15), SM 32 may proceed to step 1508. In step 1508, SM 32 may set a welded-contactor flag. By setting the welded-contactor flag, SM 32 may indicate that compressor 12 may have at least one welded contactor. In such case, power may be delivered to compressor 12, due to the welded contactor, despite the attempt of CM 30 or SM 32 to deactivate compressor 12. The welded-contactor flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly. Specifically, CM 30 may activate compressor 12 while it is in the welded-contactor state to avoid a voltage imbalance condition and prevent damage or overheating of compressor 12. Further, CM 30 or system controller 34 may notify a user that compressor 12 is being operated in a welded-contactor state.

Referring now to FIG. 16, a flow chart illustrating an algorithm 1600 for SM 32 to detect a locked rotor condition is shown. Algorithm 1600 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. In a locked rotor condition, a rotor of the electric motor may be seized. Normally, when an electric motor is activated, electric current of the motor (I) increases for an initial period during startup, and then decreases as the motor reaches operating speed. If, however, the rotor is seized, I will not decrease after the initial period. Prior to execution of the algorithm 1600, a locked-rotor flag may have been reset by SM 32.

In step 1601, SM 32 may buffer electrical current measurements for a predetermined buffer period. For example, SM 32 may buffer electrical current measurements for 200 ms.

In step 1602, SM 32 may determine whether I is greater than a minimum electric current threshold (I_(min-16)). When I is not greater than I_(min-16), SM 32 may loop back to step 1601 and continue to buffer I. In step 1602, when SM 32 determines that I is greater than I_(min-16), SM 32 may proceed to step 1604.

In step 1604, SM 32 may determine the greatest I value currently in the buffer (I_(grtst-16)). In step 1606, SM 32 may determine whether I_(grtst) is greater than an electric current threshold (I_(max-16)). SM 32 may then wait in steps 1608 and 1610 for a time threshold (TM_(Thr-16)) to expire. For example, Tm_(Thr-16) may be set to two seconds. In this way, SM 32 allows I to settle to a normal operating current if the electric motor does not have a locked rotor.

When I_(grtst-16) is greater than I_(max-16) in step 1606, then in step 1612, SM 32 may use I_(max-16) as the current threshold. In step 1612, when I is greater than I_(max-16), SM 32 may determine that a locked rotor condition exists and may proceed to step 1614 to set the locked-rotor flag. In step 1612, when I is not greater than I_(max-16), SM 32 may end execution of the algorithm in step 1616.

In step 1606, when I_(grtst-16) is not greater than I_(max-16), SM 32 may use a predetermined percentage (X %) of I_(grtst-16) as the current threshold in step 1618. In step 1618, when I_(mtr-16) is greater than X % of I_(grtst-16), SM 32 may determine that a locked rotor condition exists and may set the locked-rotor flag in step 1614. SM 32 may end execution of the algorithm in step 1616. The locked-rotor flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

If a locked-rotor condition is detected a predetermined number of consecutive times, SM 32 may set a locked rotor lockout flag. SM 32 may cease operation of the compressor until the lockout flag is cleared by a user. For example, SM 32 may set the locked rotor lockout flag when it detects ten consecutive locked rotor conditions.

Referring now to FIG. 17, a flow chart illustrating an algorithm 1700 for SM 32 to detect a motor protection trip is shown. Algorithm 1700 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. Compressor 12 may be configured with internal line breaks. The internal line breaks may trip, or deactivate, compressor 12 when electric current is excessive or when compressor 12 is overheating. In such case, SM 32 may detect that an internal line break has occurred and notify CM 30. Prior to execution of the algorithm 1700, a protection-trip flag may have been reset by SM 32.

In step 1701, SM 32 determines whether any voltage, V₁, V₂, or V₃ is greater than a voltage minimum threshold (V_(min-17)). When V₁, V₂, or V₃ is not greater than V_(min-17), SM 32 may end execution of algorithm 1700 in step 1702. When V₁, V₂, or V₃ is greater than V_(min-17), SM 32 may proceed to step 1704. In step 1704, SM 32 may determine whether I is less than a current minimum I_(min-17). When I is not less than I_(min-17), SM 32 may end execution of algorithm 1700 in step 1702. When I is less than I_(min-17), SM 32 may proceed to step 1706 and set a protection-trip flag. In this way, when voltage is present, but electric current is not present, SM 32 may determine that an internal line break condition has occurred. The protection-trip flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

Referring now to FIG. 18, a flow chart illustrating an algorithm 1800 for SM 32 to detect a low voltage condition is shown. Algorithm 1800 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. Prior to execution of the algorithm 1800, a low-voltage flag may have been reset by SM 32.

In step 1801, SM 32 may determine the normal operating voltage of compressor (V_(nml)). SM 32 may determine V_(nml) based on historical data of previous compressor operating voltages. For example, V_(nml) may be calculated by averaging the voltage over the first five electrical cycles of power during the first normal run. V_(nml) may alternatively be predetermined and stored in ROM 104, 124, or calculated based on an average voltage over the operating life of the compressor.

In step 1802, SM 32 may monitor V_(1,2, and 3) for a predetermined time period TM_(thr-18). For example, Tm_(Thr-18) may be set to two seconds. The time threshold may or may not be the same as the time threshold used in other diagnostic algorithms. In step 1804, SM 32 may determine whether V_(1, 2, and 3) are less than a predetermined percentage (X %) of V_(nml) for more than TM_(thr-18). For example, the predetermined percentage may be 75 percent. In step 1804, when V_(1, 2, and 3) are not less than X % of V_(nml) for more than TM_(thr-18), SM 32 loops back to step 1802. In step 1804, when V_(1, 2, and 3) are less than X % of V_(nml) for more than TM_(thr-18), SM 32 may proceed to step 1806.

In step 1806, SM 32 may determine whether the run state is set to run. When the run state is not set to run in step 1806, SM 32 ends execution of algorithm 1800 in step 1808. When the run state is set to run, SM 32 may determine that a low-voltage condition exists and may set a low-voltage flag in step 1810. The low-voltage flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

Referring now to FIG. 19, a flow chart illustrating an algorithm 1900 for SM 32 to detect a phase loss condition for compressor 12, when three phase electric power 50 is used. Algorithm 1900 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. SM 32 may compare each voltage, V₁, V₂, and V₃, to determine whether any particular voltage is lower than a predetermined percentage of the average of the other two voltages. Prior to execution of the algorithm 1900, a phase-loss flag may have been reset by SM 32

In step 1901, SM 32 may monitor V₁, V₂, and V₃. In step 1902, SM 32 may determine whether V₁ is less than a predetermined percentage, X %, of the average of V₂ and V₃, for a time (Tm) greater than a time threshold, Tm_(thr-19). When V₁ is less than X % of the average of V₂ and V₃, SM 32 may set the phase-loss flag in step 1904 and end execution of algorithm 1900 in step 1906. When V₁ is not less than X % of the average of V₂ and V₃, SM 32 may proceed to step 1908.

In step 1908, SM 32 may determine whether V₂ is less than X % of the average of V₁ and V₃, for Tm greater than Tm_(Thr-19). When V₂ is less than X %, of the average of V₁ and V₃, SM 32 may set the phase-loss flag in step 1904 and end execution of algorithm 1900 in step 1906. When V₂ is not less than X % of the average of V₁ and V₃, SM may proceed to step 1910.

In step 1910, SM 32 may determine whether V₃ is less than X % of the average of V₁ and V₂, for Tm greater than Tm_(Thr-19). When V₃ is less than X %, of the average of V₁ and V₂, SM 32 may set the phase-loss flag in step 1904 and end execution of algorithm 1900 in step 1906. When V₃ is not less than X % of the average of V₁ and V₂, SM 32 may loop back to step 1901. In this way, algorithm 1900 may operate concurrently with algorithm 1300. The phase-loss flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

If a phase-loss condition is detected a predetermined number of consecutive times, SM 32 may set a phase-loss lockout flag. SM 32 may cease operation of the compressor until the lockout flag is cleared by a user. For example, SM 32 may set the phase-loss lockout flag when it detects ten consecutive phase-loss conditions.

Referring now to FIG. 20, a flow chart illustrating an algorithm 2000 for SM 32 to detect a voltage imbalance condition for compressor 12, when three phase electric power 50 is used. Algorithm 2000 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. SM 32 may determine whether the difference between any of voltages V₁, V₂, or V₃ is greater than a predetermined percentage of the average of V₁, V₂, and V₃. When the difference between any of voltages V₁, V₂, or V₃ is greater than a predetermined percentage of the average of V₁, V₂, and V₃, SM 32 may determine that a voltage imbalance condition exists. Prior to execution of the algorithm 2000, a voltage-imbalance flag may have been reset by SM 32

In step 2001, SM 32 may monitor V₁, V₂, and V₃. In step 2002, SM 32 may calculate the average (V_(avg)) of V₁, V₂, and V₃. In step 2004, SM 32 may calculate the percentage of voltage imbalance (% V_(imb)) by determining the maximum of the absolute value of the difference between each of V₁ and V_(avg), V₂ and V_(avg), and V₃ and V_(avg). The maximum difference is then multiplied by V_(avg)/100.

In step 2006, SM 32 determines whether the run state is set to run. In step 2006, when the run state is not set to run, SM 32 may end execution of algorithm 2000 in step 2008. In step 2006, when the run state is set to run, SM 32 may proceed to step 2010.

In step 2010, SM 32 may determine whether % V_(imb) is greater than a voltage imbalance threshold (% V_(Thr-20)). When % V_(imb) is not greater than % V_(Thr-20), SM 32 loops back to step 2001. In this way, algorithm 2000 may execute concurrently with operating algorithm 1300. When % V_(imb) is greater than % V_(Thr-20), a voltage imbalance condition exists, and SM 32 may set the voltage-imbalance flag in step 2012. SM 32 may end execution of algorithm 2000 in step 2008. The voltage-imbalance flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

Referring now to FIG. 21, a flow chart illustrating an algorithm 2100 for SM 32 to detect a current overload condition is shown. Algorithm 2100 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. Prior to execution of the algorithm 2100, a current-overload flag may have been reset by SM 32

In step 2101, SM 32 may determine the maximum continuous current (MCC) for the electric motor of compressor 12. MCC may be predetermined and set during the manufacture of compressor 12. MCC may be stored in ROM 104 and/or embedded ROM 124. In addition, MCC may be user configurable. MCC may vary based on the type of refrigerant used. Thus, a user of compressor 12 may modify the default MCC value to conform to actual refrigeration system conditions.

In step 2102, SM 32 may determine whether the run state is set to run. When the run state is not set to run, SM 32 ends execution of algorithm 2100 in step 2104. In step 2102, when the run state is set to run, SM 32 may proceed to step 2106. In step 2106, when run state has not been set to run for a time period greater than a first time threshold (TM_(Thr1-21)), SM 32 loops back to step 2102. In step 2106, when run state has been set to run for a time period greater than TM_(Thr1-21), SM 32 may proceed to step 2108.

In step 2108, SM 32 monitors I. In step 2110, SM 32 may determine whether I is greater than MCC multiplied by 1.1. In other words, SM 32 may determine whether I is greater than 110% of MCC for a time greater than a second time threshold (TM_(Thr2-21)). When SM 32 determines that I is not greater than 110% of MCC for a time greater than TM_(Thr2-21), SM 32 may loop back to step 2102. In this way, algorithm 2100 may execute concurrently with operating algorithm 1300. When SM 32 determines that I is greater than 110% of MCC for a time greater than TM_(Thr2-21), SM 32 may determine that a current-overload condition exists and may set the current-overload flag in step 2112. SM 32 may end execution of the algorithm 2100 in step 2104. The current-overload flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

Referring now to FIG. 22, a flow chart illustrating an algorithm 2200 for SM 32 to detect a current delay condition, in a two current sensor system, to detect a lag between two electrical currents I₁ and I₂. Algorithm 2200 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. Prior to execution of the algorithm, a current-delay flag may have been reset by SM 32.

When SM 32 detects current greater than a current threshold (I_(min-22)) from one of the two current sensors, SM 32 may determine whether current indicated by the other current sensor becomes greater than I_(min-22) within a time period threshold (Tm_(Thr-22)). In step 2201, SM 32 may determine whether is greater than a current threshold I_(min-22). When I₁ is greater than I_(min-22), SM 32 may proceed to step 2203 and start a time counter (Tm). SM 32 may proceed to step 2205 to determine whether I₂ is greater than I_(min-22). In step 2205, when I₂ is greater than I_(min-22), SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2210. In step 2205, when I₂ is not greater than I_(min-22), SM 32 may proceed to step 2207 and determine whether Tm is greater than Tm_(Thr-22). In step 2207, when TM is not greater than TM_(Thr-22), SM 32 may loop back to step 2205 to compare I₂ with I_(min-22). In step 2207, when Tm is greater than Tm_(Thr-22), the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2209 to set a current-delay flag. SM 32 may end execution of the algorithm 2200 in step 2210. The current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

When I₁ is not greater than I_(min-22), SM 32 may proceed to step 2202 and determine whether I₂ is greater than I_(min-22). When I₂ is not greater than I_(min-22), SM 32 loops back to step 2201. When I₂ is greater than I_(min-22), SM 32 may proceed to step 2204 to start time Tm counter. SM 32 may proceed to step 2206 to determine whether I₁ is greater than I_(min-22). In step 2206, when I₁ is greater than I_(min-22), SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2210. In step 2206, when I₁ is not greater than I_(min-22), SM 32 may proceed to step 2208 and determine whether Tm is greater than Tm_(Thr-22). In step 2208, when TM is not greater than TM_(Thr-22), SM 32 may loop back to step 2206 to compare I₁ with I_(min-22). In step 2208, when Tm is greater than Tm_(Thr-22), the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2209 to set the current-delay flag. SM 32 may end execution of the algorithm 2200 in step 2210. As noted above, the current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34, which may adjust compressor and refrigeration system operation accordingly.

Referring now to FIG. 23, a flow chart illustrating an algorithm 2300 for SM 32 to detect a current delay condition is shown, in a three current sensor system, to detect a lag between three electrical currents I₁, I₂, and I₃. Algorithm 2300 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of FIG. 13 above. Prior to execution of the algorithm, a current-delay flag may have been reset by SM 32.

When SM 32 detects current greater than a current threshold (I_(min-22)) from one of the three current sensors, SM 32 may determine whether current indicated by the other current sensors becomes greater than I_(min-22) within a predetermined time period (Tm_(Thr-22)). In step 2301, SM 32 may determine whether I₁ is greater than a current threshold I_(min-22). When I₁ is greater than I_(min-22), SM 32 may proceed to step 2302 and start a time counter (Tm). SM 32 may proceed to step 2303 to determine whether I₂ and I₃ are greater than I_(min-22). In step 2303, when I₂ and I₃ are greater than I_(min-22), SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2304. In step 2303, when I₂ and I₃ are not greater than I_(min-22), SM 32 may proceed to step 2305 and determine whether Tm is greater than Tm_(Thr-22). In step 2305, when TM is not greater than TM_(Thr-22), SM 32 may loop back to step 2303 to compare I₂ and I₃ with I_(min-22). In step 2305, when Tm is greater than Tm_(Thr-22), the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2306 to set a current-delay flag. SM 32 may end execution of the algorithm 2300 in step 2304. The current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

In step 2301, when I₁ is not greater than I_(min-22), SM 32 may proceed to step 2307 and determine whether I₂ is greater than I_(min-22). When I₂ is greater than I_(min-22), SM 32 may proceed to step 2308 to start Tm counter. SM 32 may proceed to step 2309 to determine whether I₁ and I₃ are greater than I_(min-22). In step 2309, when I₁ and I₃ are greater than I_(min-22), SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2304. In step 2309, when I₁ and I₃ are not greater than I_(min-22), SM 32 may proceed to step 2310 and determine whether Tm is greater than Tm_(Thr-22). In step 2310, when TM is not greater than TM_(Thr-22), SM 32 may loop back to step 2309 to compare I₁ and I₃ with I_(min-22). In step 2310, when Tm is greater than Tm_(Thr-22), the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2306 to set the current-delay flag. SM 32 may end execution of the algorithm 2300 in step 2304. As noted above, the current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34, which may adjust compressor and refrigeration system operation accordingly.

In step 2307, when I₂ is not greater than I_(min-22), SM 32 may proceed to step 2311 and determine whether I₃ is greater than I_(min-22). When I₃ is not greater than I_(min-22), SM 32 may loop back to step 2301. When I₃ is greater than I_(min-22), SM 32 may proceed to step 2312 to start Tm counter. SM 32 may proceed to step 2313 to determine whether I₁ and I₂ are greater than I_(min-22). In step 2313, when I₁ and I₂ are greater than I_(min-22), SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2304. In step 2313, when I₁ and I₂ are not greater than I_(min-22), SM 32 may proceed to step 2314 and determine whether Tm is greater than Tm_(Thr-22). In step 2314, when TM is not greater than TM_(Thr-22), SM 32 may loop back to step 2313 to compare I₁ and I₂ with I_(min-22). In step 2314, when Tm is greater than Tm_(Thr-22), the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2306 to set the current-delay flag. SM 32 may end execution of the algorithm 2300 in step 2304. As noted above, the current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34, which may adjust compressor and refrigeration system operation accordingly.

With respect to each of the diagnostic algorithms described above with reference to FIGS. 14 to 23, SM 32 may selectively execute the diagnostic algorithms as needed and as data for the diagnostic algorithms is available. When a communication link is not available, or when data from a connected sensor is not available, due to malfunction or otherwise, SM 32 may disable those portions of the diagnostic algorithms that require the missing communication link or data. In this way, SM 32 may execute those portions of the diagnostic algorithms that are executable, based on the data and communication link(s) available to SM 32.

In this way, SM 32 may monitor electrical current and voltage measurements, make data calculations based on the electrical current and voltage measurements, and execute diagnostic algorithms based on the measurements and based on the calculations. SM 32 may communicate the measurements, the calculations, and the results of the diagnostic algorithms to CM 30 or system controller 34. SM 32 may thereby be able to provide efficient and accurate electrical power measurements and calculations to be utilized by other modules and by users to evaluate operating conditions, power consumption, and efficiency. 

What is claimed is:
 1. A sensor module for a compressor having an electric motor connected to a power supply, the sensor module comprising: an input that receives current measurements generated by a current sensor based on a current of the power supply; and a processor that is connected to the input, that determines a maximum continuous current for the electric motor set based on a type of refrigerant used by the compressor, and that selectively compares the current measurements with a value equal to the maximum continuous current multiplied by a predetermined value.
 2. A system comprising: the sensor module of claim 1; and an electrical enclosure that is configured to house electrical terminals for connecting the power supply with the electrical motor, wherein the sensor module is disposed within the electrical enclosure.
 3. The sensor module of claim 1 wherein the processor determines whether to compare the current measurements with the value based on a period that the compressor has been in a run state.
 4. The sensor module of claim 3 wherein the processor compares the current measurements with the value in response to a determination that the period is greater than a predetermined period.
 5. The sensor module of claim 4 wherein the processor disables the comparison in response to a determination that the period is less than the predetermined period.
 6. The sensor module of claim 1 wherein the processor determines whether to compare the current measurements with the value based on whether the compressor is in a run state.
 7. The sensor module of claim 6 wherein the processor: disables the comparison of the current measurements with the value when the compressor is not in the run state; disables the comparison of the current measurements with the value when a period of operation of the compressor in the run state is less than a predetermined period; and compares the current measurements with the value when the period of operation of the compressor in the run state is greater than the predetermined period.
 8. The sensor module of claim 1 wherein the maximum continuous current for the electric motor is set during manufacture of the compressor.
 9. The sensor module of claim 8 wherein the maximum continuous current for the electric motor is user configurable.
 10. The sensor module of claim 1 further comprising memory that stores the maximum continuous current.
 11. The sensor module of claim 1 wherein the predetermined value is equal to 1.1.
 12. A system comprising: the sensor module of claim 1, wherein the sensor module sets a flag when the current measurements are greater than the value for a predetermined period; and at least one of a control module and a system controller that selectively adjusts at least one of compressor and refrigeration system operation based on the setting of the flag.
 13. A sensor module for a compressor having an electric motor connected to a power supply, the sensor module comprising: an input that receives current measurements generated by a current sensor based on a current of the power supply; and a processor that is connected to the input, that determines a maximum continuous current for the electric motor set based on actual refrigeration system conditions, and that selectively compares the current measurements with a value equal to the maximum continuous current multiplied by a predetermined value.
 14. The sensor module of claim 13 wherein the predetermined value is equal to 1.1.
 15. A method performed by a sensor module for a compressor having an electric motor connected to a power supply, the method comprising: receiving current measurements generated by a current sensor based on a current of the power supply; determining a maximum continuous current for the electric motor set based on at least one of a type of refrigerant used by the compressor and actual refrigeration system conditions; and selectively comparing the current measurements with a value equal to the maximum continuous current multiplied by a predetermined value.
 16. The method of claim 15 further comprising determining whether to compare the current measurements with the value based on a period that the compressor has been in a run state.
 17. The method of claim 16 further comprising comparing the current measurements with the value in response to a determination that the period is greater than a predetermined period.
 18. The method of claim 17 further comprising disabling the comparison in response to a determination that the period is less than the predetermined period.
 19. The method of claim 15 further comprising determining whether to compare the current measurements with the value based on whether the compressor is in a run state.
 20. The method of claim 19 further comprising: disabling the comparison of the current measurements with the value when the compressor is not in the run state; disabling the comparison of the current measurements with the value when a period of operation of the compressor in the run state is less than a predetermined period; and comparing the current measurements with the value when the period of operation of the compressor in the run state is greater than the predetermined period.
 21. The method of claim 15 further comprising setting the maximum continuous current for the electric motor during manufacture of the compressor.
 22. The method of claim 21 further comprising setting the maximum continuous current for the electric motor based on user input.
 23. The method of claim 15 further comprising storing the maximum continuous current in memory of the sensor module.
 24. A method of claim 15 further comprising: setting a flag when the current measurements are greater than the value for a predetermined period; and, using at least one of a control module and a system controller, selectively adjusting at least one of compressor and refrigeration system operation based on the setting of the flag.
 25. The method of claim 15 wherein the predetermined value is equal to 1.1. 